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https://doi.org/10.22214/ijraset.2021.39009
November 2021
International Journal for Research in Applied Science & Engineering Technology (IJRASET) ISSN: 2321-9653; IC Value: 45.98; SJ Impact Factor: 7.429 Volume 9 Issue XI Nov 2021- Available at www.ijraset.com
Seismic Response of Large span slab in Horizontal Setback Building Manish Kumar Pandey1, Dr. Raghvendra Singh2 1
P.G. Scholar, 2Professor, Civil Engineering Department, Ujjain Engineering College Ujjain, M.P., India
Abstract: The demand for multi-storey buildings is increasing day by day. Residential plus commercial building is mainly used for wide span needs. Wide span required for Flat slab, Waffle slab and ribbed slab stands An excellent option for architects when larger openings in a building need to be covered with as few columns as possible. The use of different types of plates is developing as a new trend and is becoming a major challenge for structural engineers. Therefore, it is necessary to study about its structural behavior. The project is carried out under earthquake zone III under the earthquake analysis of G+9 storey building. For this study, four different types of large span slab structure are modelled in C-shape (Horizontal Setback Building) having 10-stories i.e. G+9 storied buildings with 3.50 meters height for each story is modelled and analysed. The plan area of all four buildings is same i.e. 2859 square meters (49.50 m x 82.50 m) each. These buildings were designed in compliance with the Indian Code of Practices for earthquake resistant design of buildings. Base of the building were fixed. The square sections are used for structural elements. The height of the buildings is considered constant throughout the structure. The buildings are modelled using ETABSvr.2016. Keywords: large span slab, ETABSvr.2016, Horizontal Setback Building, Flat slab, Waffle slab and ribbed slab I. INTRODUCTION I Horizontal setback buildings are prone to suffer significant damage during seismic excitation due to in-plane soil flexibility, which affects performance in two ways: the first one is change the lateral force distribution between the lateral load-bearing members; and second one is causes excessive stress concentration at the re entrant corners. Recoil structures are highly susceptible during earthquakes due to their vertical geometric and mass irregularity, but the fragility is further increased if the structures also have stiffness irregularities. If the structure is on a sloping ground, the risk factor of this structure may increase. In this paper, the seismic performances of regression structures sitting on flat ground as well as on the slope of a hill with a soft storey configuration were evaluated. The analysis was carried out in three different methods, namely the equivalent static force method, the response spectrum method and the time domain method, and the extreme responses were recorded for the open ground storey inverted building. To reduce this soft fold effect and overreactions, three different reduction techniques were adopted and the best solution from these three techniques was presented. The horizontal setback building consist is also enhance the effect of the building under various types of slabs are used. The Slabs are constructed to provide flat surfaces, usually horizontal in building floors, roofs, bridges, and other types of structures. The slab may be supported by walls or by reinforced concrete beams usually cast monolithically with the slab or by structural steel beams or by columns, or by the ground. The basically slabs are used as normal, waffle, ribbed and waffle slab. II. The following objectives are taken in this project
OBJECTIVES OF THE PROJECT
1) To study the behavior of different types of slab & secondary beam in a structure. 2) To Study the various past research based on use of various slabs and secondary beam.. 3) To Modelled a G+9 multistory building under taking different variation on slabs & introduce a secondary beam in the structure. 4) To compare a different models case to find optimized structure. 5) To analysis G+9 multistory building by RSA (Response Spectrum Analysis). 6) To assist the different parametric result such as Storey displacement, base shear, overturning moments, storey shears etc into it.
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International Journal for Research in Applied Science & Engineering Technology (IJRASET) ISSN: 2321-9653; IC Value: 45.98; SJ Impact Factor: 7.429 Volume 9 Issue XI Nov 2021- Available at www.ijraset.com III. METHODOLOGY AND MODELLING Modeling and analysis of this research is done in CSi ETABS software. For complex structural analysis, a software like CSi ETABS helps in visualization of the structural model and also deprive the tedious calculation of the analysis results in complex structures like the structures under consideration in this study. The table 1 is explained the model cases used on in this project.
S. No. 01 02 03 04
Table 1: Model Description Model Description Structure Description Model 1 Building having Flat Slab with Drop Panels Model 2 Building having Waffle Slab Model 3 Building having Ribbed Slab Model 4 Building having Secondary Beams
A. Structural & Material Properties Table 2 and 3 enlist the structural and material properties respectively. Table 2: Structural Properties S. No. A) 1 2 3 4 5 6 8 B) 1 2 3 4 5 C) 1 2 3 4 5 6 D) 1 2 3 4 5 E) 1 2 3 5
Structural Properties Descriptions Of Parameters Common Parameters Structure type No of storey /total height Plan area Column size Spacing in grid in x –direction Spacing in grid in y –direction Individual storey height Model 1: Building Having Flat Slab with Drops Beam Size Slab Thickness without Drop Slab thickness with Drops Drop Size Thickness of Drops Model 2: Building Having Waffle Slab Beam Size Slab Thickness Overall Slab thickness Stem Width Spacing of Stems in X-Direction Spacing of Stems in Y-Direction Model 3: Building Having Ribbed Slab Beam Size Slab Thickness Overall Slab thickness Stem Width Spacing of Stems in X-Direction Model 4: Building Having Secondary Beams Beam Size Slab Thickness Secondary Beam Size Spacing of Beams in X-Direction
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Dimensions / Comments Rigid frame Buiding G+9 /35.00 m 49.50 m x 82.50 m 600 mm x 600 mm 8.25 m. c/c 8.25 m. c/c 3.50 m. No beams 285 mm 360 mm 3.00 m x 3.00 m 75 mm 400 mm x 700 mm 150 mm 450 mm 250 mm 1500 mm c/c 1500 mm c/c 400 mm x 700 mm 150 mm 450 mm 250 mm 1500 mm c/c 400 mm x 700 mm 150 mm 250 mm x 400 mm 2000 mm c/c
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International Journal for Research in Applied Science & Engineering Technology (IJRASET) ISSN: 2321-9653; IC Value: 45.98; SJ Impact Factor: 7.429 Volume 9 Issue XI Nov 2021- Available at www.ijraset.com Table 3: Material Properties Material Properties S. No.
Types of material
Dimensions / comments
1
Concrete ( beam & column)
M-30
2
Concrete ( Slab)
M-25
3
Grade of rebar (R/F)
HYSD-500
Figure 1 and figure 2 represent the Plan and 3-D view of the Model 1 & 2. Figure 3. to figure 4 depicts the plan and 3d of each model similarly.
Fig. 1: Model 1: Building with Flat Slab a) Plan
Fig. 2: Model 2 Building with Waffle Slab a) Plan
b) 3D model
b) 3D model
Fig. 3: Model 3: Building with Ribbed Slab a) Plan
b) 3D model
Fig. 4: Model 4: Building with Secondary Beams a) Plan
b) 3D model
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International Journal for Research in Applied Science & Engineering Technology (IJRASET) ISSN: 2321-9653; IC Value: 45.98; SJ Impact Factor: 7.429 Volume 9 Issue XI Nov 2021- Available at www.ijraset.com IV. RESULTS AND DISCUSSION Based on the modelling the lists out results are taken from the software analysis of all four models with the concept of horizontal setback approach. The results are as follows: A. Storey Displacement Deflection of the stories from the initial position is termed as storey displacements and its maximum value is obtained at the top storey. The values of storey displacements in X and Y directions obtained from the analysis has been shown in table and table respectively, while graphical representation is described in fig 5 and fig 6 for X and Y direction respectively. Table 4 and 5 show the storey result in x and y Direction . Table 4: Storey Displacement in X-Direction (mm) S.N.
Stories
Model 1
Model 2
Model 3
Model 4
1
G+9
125.641
82.874
67.02
71.603
2
G+8
121.142
80.122
64.596
68.604
3
G+7
113.991
75.47
60.935
64.08
4
G+6
104.35
69.191
56.324
58.361
5
G+5
92.663
61.626
50.974
51.71
6
G+4
79.396
53.086
45.068
44.352
7
G+3
64.977
43.844
38.762
36.486
8
G+2
49.793
34.13
32.192
28.28
9
G+1
34.242
24.143
25.46
19.881
10
G+0
18.947
14.098
18.599
11.477
11
Ground
5.599
4.632
11.082
3.678
Storey Displacement in X-Direction (mm) Ground G+0 G+1 G+2 G+3 G+4 G+5 G+6 G+7 G+8 G+9
Model 4 Model 3 Model 2 Model 1
0
50
100
150
Fig 5: Storey Displacement in X-Direction
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International Journal for Research in Applied Science & Engineering Technology (IJRASET) ISSN: 2321-9653; IC Value: 45.98; SJ Impact Factor: 7.429 Volume 9 Issue XI Nov 2021- Available at www.ijraset.com
Table 5: Storey Displacement in Y-Direction (mm) S.N.
Stories
Model 1
Model 2
Model 3
Model 4
1
G+9
125.828
83.66
76.382
71.106
2
G+8
121.298
80.82
73.58
68.078
3
G+7
114.115
76.079
69.388
63.552
4
G+6
104.444
69.709
64.099
57.852
5
G+5
92.73
62.053
57.954
51.235
6
G+4
79.439
53.423
51.163
43.929
7
G+3
64.999
44.095
43.909
36.127
8
G+2
49.798
34.303
36.343
27.998
9
G+1
34.236
24.247
28.577
19.688
10
G+0
18.936
14.141
20.612
11.377
11
Ground
5.593
4.636
11.807
3.657
Storey Displacement in Y-Direction (mm) Ground G+0 G+1 G+2 G+3 G+4 G+5 G+6 G+7 G+8 G+9
Model 4 Model 3 Model 2 Model 1
0
50
100
150
Fig 6: Storey Displacement in Y-Direction From above representation it is clear that the Storey displacement is nearly equal in both the direction i.e. X and Y for all the models. Model 1 (Building having Flat Slab with Drop Panels) shows higher storey displacement than other models and lowest value of storey displacement has been obtained in Model 3 (Building having Ribbed Slab) and Model 4 (Building having Secondary Beams).
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International Journal for Research in Applied Science & Engineering Technology (IJRASET) ISSN: 2321-9653; IC Value: 45.98; SJ Impact Factor: 7.429 Volume 9 Issue XI Nov 2021- Available at www.ijraset.com B. Base Shear and Overturning Moment Maximum shear force at the base of the structure is termed as base shear. Similarly the moment at the base of the structure is known as overturning moment. Both the quantity depends on the magnitude of lateral forces and dead weight of the structure. Based on the analysis results base shear and overturning moments are shown in table 4.3. Table 6:Base Shear and Overturning Moment S.N.
Model
Fx (kN)
Fy (kN)
Mz (kN-m)
1
Model 1
13501.30
13487.39
610205.92
2
Model 2
19132.77
19037.14
864381.30
3
Model 3
13981.33
12339.74
560285.76
4
Model 4
13574.61
13713.20
622647.78
A bar chart representation of base shear and overturning moment is shown in Fig 4.3 and 4.4 respectively.
Base Shear (kN) 20000 15000 Fx (kN)
10000
Fy (kN) 5000 0 Model 1 Model 2 Model 3 Model 4 Fig 7: Bar chart comparison of Base Shear
Mz (kN-m) 1000000 800000 600000 Mz (kN-m) 400000 200000 0 Model 1 Model 2 Model 3 Model 4 Fig 8: Bar chart comparison of Overturning Moments Model 2 depicts higher base shear in both the direction as well as overturning moments in Z-direction. Model 1 and Model 3 shows lowest base shear in x-direction and Y-direction respectively.
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International Journal for Research in Applied Science & Engineering Technology (IJRASET) ISSN: 2321-9653; IC Value: 45.98; SJ Impact Factor: 7.429 Volume 9 Issue XI Nov 2021- Available at www.ijraset.com C. Storey Acceleration Storey Acceleration is a dynamic perimeter for the seismic analysis of structures, which shows the acceleration of building under dynamic seismic loading. Table 4.4 shows the value of acceleration for different cases under consideration in this study. Fig 4.5 depicts the bar chart representation of the structures. Table 4.3: Storey Acceleration (mm/sec2 ) S.N.
Acceleration
Model Ux
Uy
Uz
1
Model 1
203.32
460.14
29.10
2
Model 2
299.63
674.16
16.76
3
Model 3
321.03
738.37
18.83
4
Model 4
331.73
738.37
24.46
Storey Acceleration (mm/sec2) 800 700 600 500 Acceleration Ux
400
Acceleration Uy
300
Acceleration Uz
200 100 0 Model Model Model Model 1 2 3 4 Fig 4.6: Storey Acceleration
Model 4 shows highest value of storey acceleration in all three directions while Model 1 shows lowest value of storey acceleration in X and y direction. In Z direction lowest value has been observed in Model 2. V. CONCLUSIONS On The basis of above study on “Seismic Response of Large span slab in Horizontal Setback Building” in which four cases of same storied and height structures has been taken under consideration as defined earlier, following results are concluded. A. Model 3 and Model 4 i.e. structures having ribbed slab and secondary beams show less storey displacement than other models. B. Model 1 (Building having Flat Slab with Drop Panels) shows higher magnitude of storey displacement which is nearly 1.7 to 1.8 of Model 3 and Model 4. C. Base shear and Overturning moments are nearly identical in Model 1 and Model 4 while Model 2 shows highest value of base shear and overturning moment which almost 1.5 times of the Model 1 and model 4. D. Model 2 shows least storey accelartion amng all four structures while maximum storey acceleration is obtained in Model 4 which is nearly 1.5 to 1.6 of the lowest value. E. Most preferable long span slab on the basis of this study is Building with Waffle or ribbed Slab.
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International Journal for Research in Applied Science & Engineering Technology (IJRASET) ISSN: 2321-9653; IC Value: 45.98; SJ Impact Factor: 7.429 Volume 9 Issue XI Nov 2021- Available at www.ijraset.com REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]
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